The present invention relates to digital radio communications apparatus comprising a base unit and a plurality of handsets communicable with the base unit.
FIG. 22 is a block diagram showing related art radio telephone apparatus as related art digital radio communications apparatus.
In FIG. 22, a numeral 100 designates a base unit, 101 a radio section for communicating with handsets 200, 210 mentioned later, 102 an antenna, and 103 a controller for controlling the components of the digital radio communications apparatus. The components 101 through 103 constitute the base unit 100 of the digital radio communications apparatus. A numeral 200 designates a handset, 201 a radio section for communicating with the base unit 100 or another handset 210 (mentioned later), 202 an antenna, 203 a base unit communications controller for establishing and releasing communications with the base unit 100, 204 a direct inter-handset communications controller for establishing and releasing direct inter-handset communications, and 206 a basic controller for controlling the components 201 through 204. The components 201 through 206 constitute the handset 200 of the digital radio communications apparatus. A numeral 210 designates a handset, 211 a radio section for communicating with the base unit 100 or another handset 200, 212 an antenna, 213 a base unit communications controller for establishing and releasing communications with the base unit 100, 214 a direct inter-handset communications controller for establishing and releasing direct inter-handset communications, and 216 a basic controller for controlling the components 211 through 214. The components 211 through 216 constitute the handset 210 of the digital radio communications apparatus.
A series of operations from inter-handset communications via the base unit 100 to direct inter-handset communications will be explained using FIG. 23. FIG. 23 is a sequence diagram showing an operation of the digital radio communications apparatus of FIG. 22.
In FIG. 23, in case the handset 200 starts direct inter-handset communications with the handset 210 from a state where the handsets 200 and the handsets 210 are synchronized with the base unit 100, the basic controller 206 of the handset 200 activates the base unit communications controller 203 and transmits a Call Request message to the base unit 100 (S100). The Call Request message contains information on a distant party specified by the handset 210. The controller 103 of the base unit 100, receiving the Call Request message via the antenna 102 and the radio section 101, transmits an Incoming Call message to the handset 210 specified as a called number (S101). The handset 210, receiving the Incoming Call message, transmits an Incoming Call Response message to start communications with the base unit 100 in case it can respond to the call (3102). The base unit 100 which received the Incoming Call Response message and established communications with the handset 210 transmits a Call Response message to the handset 200 (S103). The handset 200, receiving the Call Response message, activates the direct inter-handset communications 204 to transmit a Direct Inter-handset Communications Transition Request message to the handset 210 via the base unit 100 (S104). The Transition Request message contains an identifier common to the handset 200 and the handset 210 used in the direct inter-handset communications. The basic controller 216 of the handset 210, receiving the Transition Request message via the base unit 100, transmits the Transition Request message to the direct inter-handset communications controller 214. The direct inter-handset communications controller 214, receiving the Transition Request message, stores the identifier common to the handset 200 and the handset 210 contained in the Transition Request message as well as transmits a Direct Inter-handset Communications Transition Accepted message to the base unit 100 via the basic controller 216, the radio section 211 and the antenna 212 (3105). The handset 200, receiving the Transition Accepted message via the base unit 100, assumes that the transition to direct inter-handset communications is accepted and transmits a Release Request Message to the base unit 100 to release communications with the base unit 100 (S106). The base unit 100, receiving the Release Request message, transmits the Release Request message to the handset 210 (S107). The handset 210, receiving the Release Request message, transmits a Release Response message to the base unit 100 to release communications with the base unit (S108). The base unit 100, receiving the Release Response message, transmits the Release Response message to the handset 200 (S109). The basic controller 206 of the handset 210 which received the Release Response message and released communications with the base unit 100 activates the direct inter-handset communications controller 204 to start transmitting control channel data via the radio section 201 and the antenna 201 (S110). In the control channel data, the identifier common to the handset 200 and the handset 210 stored by the direct inter-handset communications storage section (not shown) and identifiers specific to both handsets, that is, a new identifier generated from the identifier of the handset 200 and an identifier of the handset 210 as a called handset, are transmitted. Meanwhile, the basic controller 216 of the handset 210, releasing communications with the base unit 100, activates the direct inter-handset communications controller 214 and uses the antenna 212 and the radio section 211 to scan the data on the control channels where identifiers including the identifier common to the handset 200 and the handset 210 are transmitted. Receiving the control channel data from the handset 200, the basic controller 216 of the handset 210, checks the identifiers including the identifier common to the handset 200 and the handset 210 as well as the identifier to identify a called handset. In case the identifier to identify the called handset is the identifier of the handset 210 as a local handset, the handset 210 transmits a communications channel establishment request to the handset 200 (S111) to establish a communications channel (S112). The handset 200, establishing the communications channel, transmits a Call Request message to the handset 210 (S113). The handset 210, receiving the Call Request message, transmits a Call Accepted message to the handset 200 (S114). In this example, a transition is made from communications via the base unit 100 to direct inter-handset communications. Thus an Incoming Call Response message is automatically transmitted from the direct inter-handset communications controller 214 to the handset 200 (S115) to start direct inter-handset communications (S116).
The digital radio communications apparatus where the above control is made is disclosed for example in the Japanese Patent Laid-Open 5-167523/(1993).
However, the related art digital radio communications apparatus (digital radio telephone apparatus) once releases inter-handset communications via abase unit before establishing direct inter-handset communications and thus has a problem of taking too much time in establishing direct inter-handset communications. In case an attempt to start direct inter-handset communications results in switching to inter-handset communications via a base unit, synchronization with the base unit must be established again. Thus, this approach takes too much time and encounters release of communications.
Further, the related art digital radio communications apparatus (digital radio telephone apparatus) cannot determine whether to make a transition to direct inter-handset communications or to maintain inter-handset communications via a base unit. In case various types of data communications using direct inter-handset communications are attempted, it cannot be determined whether the distant handset supports the type of data communications desired by the calling handset due to a variety of types of data communications.